The invention relates to improvements in fluid couplings in general, and more particularly to improvements in devices which can be used to rapidly establish or terminate a sealing connection between the ends of two conduits. Still more particularly, the invention relates to improvements in couplings which are designed to establish a readily separably sealing connection between an end of a first conduit (e.g., a hose) and a second conduit (e.g., a pipe or a nipple) having an end with an at least substantially radially extending retaining portion, e.g., with an external flange having a substantially radially outwardly extending retaining surface confronting the other end of the second conduit.
German patent application Serial No. 37 41 250 of Rosch et al. (published Jun. 15, 1989) discloses a coupling which is designed to establish a sealing connection between two conduits, particularly between two conduits which serve to convey fuel in a motor vehicle. The coupling comprises a tubular coupling member a first terminal of which is connectable with an end of one of the conduits and a second terminal of which is connectable with an end of the other conduit. The coupling member carries resilient arms which can engage a retaining portion at the end of the respective conduit, and the coupling further comprises a sleeve which surrounds and is movable axially of the coupling member to and from a locking position in which the arms cannot be disengaged from the retaining portion. One or more sealing elements are interposed between at least one of the terminals and the end of the respective conduit. The external surface of the coupling member is provided with circumferentially extending grooves alternating with ribs, and the internal surface of the sleeve is also provided with alternating ribs and grooves. The sleeve is movable axially of the coupling member to any one of several positions in each of which one or more internal ribs extend into a different set of external grooves, and vice versa. This enables the coupling member to hold the sleeve against unintentional movement all the way to a position in which the coupling member can become disengaged from the retaining portion.
A drawback of the proposal of Rosch et al. is that the sleeve must be made of a material which exhibits a considerable amount of elasticity. Therefore, the assembled coupling cannot stand pronounced stresses, namely axial stresses which suffice to effect radial expansion of the sleeve with attendant expulsion of its internal ribs from the external grooves of the coupling member. Rosch et al. propose to reinforce a portion of the sleeve to prevent such unintentional forcible separation of the coupling member from one of the conduits. Reinforcement of the sleeve contributes to the cost of the coupling. Moreover, a person seeking to assemble the coupling or to separate the coupling member from one of the conduits must exert a considerable force in order to overcome the resistance of mating internal and external ribs.
U.S. Pat. No. 4,451,069 granted May 29, 1984 to Melone discloses a quick disconnect fluid coupling wherein a female member is provided with radially extending latch fingers which are designed to engage a male coupling member. The patentee proposes to employ a locking sleeve which has a set of radially resilient fingers and a ring portion movable to a position in which the fingers of the female coupling member cannot be disengaged from the male coupling member. The patentee further proposes to provide latch means for releasably holding the sleeve in the locking and release positions. The latch means comprises internal ribs on the fingers of the locking sleeve and external grooves in the male member. One of the grooves receives the internal ribs in the locking position of the sleeve, and the other groove receives the internal ribs in the release position of the sleeve. A drawback of the patented coupling is that it must employ complex (and hence expensive) male and female coupling members and a quite complicated sleeve. Moreover, the ability of the coupling to stand axial disengaging stresses is rather limited.